A novel approach to the global analysis of proton form factors in elastic electron-proton scattering

TL;DR

This paper introduces a new method for analyzing proton form factors in elastic electron-proton scattering, effectively combining data from multiple experiments with different normalization uncertainties, and addressing biases in traditional approaches.

Contribution

It proposes a novel global analysis method based on a modification of the NNPDF fitting technique, avoiding biases of the penalty trick in form factor analysis.

Findings

Minor differences from traditional fits when accounting for normalization uncertainties

Method effectively combines data from different experiments

Implications for the G_E/G_M discrepancy

Abstract

We present a novel method for the global analysis of elastic electron-proton scattering when combining data sets from experiments with different overall normalization uncertainties. The method is a modification of one employed by the NNPDF collaboration in the fitting of parton distribution data. This method is an alternative to the 'penalty trick' method traditionally employed in global fits to proton electric and magnetic form factors, while avoiding the biases inherent in that approach. We discuss issues that arise when extending the method to nonlinear models. For data with $Q^2>1$ GeV$^2$ we find relatively minor differences to traditional model fits when the normalization uncertainties from different experiments are correctly accounted for. We discuss implications of this method for the well-known discrepancy between the form factor ratio $G_E/G_M$ extracted from the Rosenbluth and polarization transfer techniques.